Epimeric mixtures of the lactone 3,6-dihydro-4,5-dimethyl-5-phenyl-alpha-pyrone

ABSTRACT

EPIMERIC MIXTURES OF THE NOVEL LACTONE 3,6-DIHYDRO4,5-DIMETHYL-5-PHENYL-A-PYRONE MAY BE PREPARED BY REACTING HYDRATROPALDEHYDE WITH ACETALDEHYDE OR CROTONALDEHYDE. THESE COMPOUNDS ARE USEFUL IN V.I. STABILIZERS IN LUBE OILS, AND AS MONOMERS IN THE PREPARATION OF POLYESTERS. UNDER CERTAIN CONDITIONS A BY-PRODUCT COMPRISING A NOVEL LINEAR CONDENSATION PRODUCT, IDENTIFIED AS AN UNSATURATED AROMATIC ALDEHYDE, IS ALSO FORMED. THE RELATIVE PROPORTIONS OF THE NOVEL LACTONE AND UNSATURATED AROMATIC ALDEHYDES THAT ARE FORMED MAY BE CONTROLLED BY VARYING THE RATIO OF HYDRATROPALDEHYDE TO ACETALDEHYDE. THE USE OF CROTONALDEHYDE INSTEAD OF ACETALDEHYDE RESULTS IN THE FORMATION OF THE NOVEL LACTONE ALONE.

United States Patent 3 825,572 EPlMERIC MlXTURES OF THE LACTONE 3,6-DI-HYDRO-4,5-DlMETHYL-5-PI'lENYL-oc-PYRONE John J. van Venrooy, Media, Pa.,assignor to Sun Research and Development Co., Philadelphia, Pa. NoDrawing. Continuation-impart of application Ser. No. 258,282, May 31,1972, now Patent No. 3,761,530. This application Dec. 26, 1972, Ser. No.318,359

Int. Cl. C07d 7/16 US. Cl. 260-3435 8 Claims ABSTRACT OF THE DISCLOSUREEpimeric mixtures of the novel lactone 3,6-dihydro-4,S-dimethyl-S-phenyl-a-pyrone may be prepared by reactinghydratropaldehyde with acetaldehyde or crotonaldehyde. These compoundsare useful in VI. stabilizers in lube oils, and as monomers in thepreparation of polyesters. Under certain conditions a by-productcomprising a novel linear condensation product, identified as anunsaturated aromatic aldehyde, is also formed. The relative proportionsof the novel lactone and unsaturated aromatic aldehydes that are formedmay be controlled by varying the ratio of hydratropaldehyde toacetaldehyde. The use of crotonaldehyde instead of acetaldehyde resultsin the formation of the novel lactone alone.

CROSS-REFERENCE TO RELATED APPLICATION This application is acontinuation-in-part of copending application Ser. No. 258,282, filedMay 31, 1972, by John J. van Venrooy, now US. Pat. No. 3,761,530.

BACKGROUND OF THE INVENTION This invention relates to certain novellactones and their preparation. More particularly, this inventionrelates to the preparation of an epimeric mixture of 3,6-dihydr0-4,5-dimethyl 5 phenyl-a-pyrones (hereinafter a-pyrone) byreacting hydratropaldehyde with acetaldehyde or crotonaldehyde in thepresence of a base. This invention further relates to the preparation ofa novel aromatic aldehyde condensation product formed under certainspecified conditions as a by-product of the aforesaid process.

In earlier-filed application, Ser. No. 258,282, filed by John J. vanVenrooy on May 31, 1972, now US. Pat. No. 3,761,530 and entitledPreparation of Polycyclic Aromatic Compounds, there is disclosed thereaction of hydratropaldehyde with propionaldehyde, in the presence of abase followed by treatment of the reaction mixture with a halogen acid.In this case, however, the product is a polycyclic1,3-dimethyl-substituted aromatic hydrocarbon. It is thus quitesurprising to find, as in the present process, that when acetaldehyde orcrotonaldehyde is substituted for propionaldehyde there is obtained alactone rather than the corresponding mono-methylatedpolycyclic-aromatic hydrocarbon.

SUMMARY OF THE INVENTION Thus, in accordance with the present invention,it has been found that when hydratropaldehyde is reacted withacetaldehyde or crotonaldehyde in the presence of a base,

3,825,572 Patented July 23, 1974 there is formed the lactone, a-pyrone,in accordance with the following equations:

These compounds are useful as V.I. stabilizers in lube oils, and asmonomers in the preparation of polyesters.

DESCRIPTION OF THE INVENTION The reaction is conveniently carried out byheating the hydratropaldehyde With the acetaldehyde or crotonaldehyde inthe presence of a base. Although dilute sodium hydroxide (about 1 to 5percent by weight of the reaction mass) is preferred, other conventionalbases of the type employed in an aldol condensation may also be used(e.g. alkali and alkaline earth metal hydroxides and carbonatesalkoxides of the alkali and alkaline earth metals and the like). Thealdehyde reagents, in an aqueous solution, and catalyst are desirablyrefluxed for about 0.5 to about 5 hours, preferably, but notessentially, under autogenons pressure.

The novel a-pyrone product is then recovered by conventional procedures,e.g. by ether extraction. The Water layer obtained from the extractionstep is desirably treated with an acid, e.g. hydrochloric acid, inamounts sufficient to neutralize the base prior to final recovery.Alterna tively, the reaction product maybe neutralized with acid priorto said ether extraction.

Drying of the ether extract yields a viscous white oil which, onstanding, solidifies to provide an epimeric mixture of3,6-dihydro-4,5-dimethyl-5-phenyl-u-pyrone.

The temperature at which the reaction is preferably carried out is thereflux temperature of the mixture, i.e. at about 95 to 105 C.Preferably, although not essentially, the reaction should be carried outunder autogenous pressure to maintain the desired ratio of reactants.

The mole ratio of acetaldehyde to hydrotropaldehyde should desirably bemaintained at about at least 1.5 to 2.5 moles of acetaldehyde for eachmole of hydratropaldehyde; preferably the mole ratio of these twoaldehydes should be about 2:1. The mole ratio of crotonaldehyde tohydratropaldehyde should be in the range of about at least 0.5 to 1.5:1, and preferably 1:1.

When the mole ratio of aldehyde reagent is varied in such a way as toprovide amounts of acetaldehyde less than that described above for eachmole of hydratropaldehyde, e.g. ratios of about 0.5 to 1.5 :1 ofacetaldehydezhydratropaldehyde, there is formed, in addition to thea-pyrone, increasing amounts of the unsaturated aromatic aldehydecondensation product of the formula III This aromatic aldehyde is usefulas plasticizers, perfume ingredients, as solvents, in pharmaceuticalsand the like.

While the mechanism of the reaction of two moles of acetaldehyde withone mole of hydratropaldehyde to yield the a-pyrone is not known withcertainty, it is believed that crotonaldehyde may be formed initially byaldol condensation of two molecules of acetaldehyde. The crotonaldehydeformed in situ then cross condenses with hydratropaldehyde resulting inthe formation of the a-pyrone. This is borne out by the facile formationof the a-pyrone directly from crotonaldehyde and hydratropaldehyde.

In order to further illustrate the invention, the following examples aregiven. In Examples 1 and 2 there are illustrated the formation of theabove-described unsaturated aromatic aldehyde as a by-product,concurrent with the formation of the a-pyrone. In the remaining exampleformation of this by-product is shown to be substantially eliminated bythe use of crotonaldehyde instead of acetaldehyde.

Example 1 To a stirred three necked flask equipped with a refluxcondenser was charged 350 ml. of water and gms. of sodium hydroxidepellets. Upon dissolution of the sodium hydroxide, 10 gms. ofhydratropaldehyde and 3.3 gms. of acetaldehyde were charged to thereactor. The reaction mixture containing acetaldehyde andhydratropaldehyde in a molar ratio of 1:1 was refluxed for two hours at98 to 100 C. The reaction mixture was extracted with ether, dried overmagnesium sulfate and the ether evaporated (the ether-extracted waterlayer containing the a-pyrone was set aside for further processing); 5.6gms. of a yellow oil were obtained. Gas chromatography showed thisportion to consist of unreacted hydratropaldehyde, a complex highboiling envelope, and a minor peak which has the highest boilingcomponent of the mixture. This component proved to be an unsaturatedaromatic aldehyde formed by the condensation of two moles ofhydratropaldehyde with one mole of acetaldehyde:

CH3 CH3 The compound C H O, having a molecular weight of 276, wasidentified via a combination of infrared and NMR spectroscopy and massspectrometry. As will be shown in further examples, this linearcondensation product may be minimized.

The water layer obtained from the above ether-extraction procedure wasneutralized with dilute hydrochloric acid and reextracted a second timewith diethylether. After drying the extract over magnesium sulfate andevaporation of the ether, 5.0 gms. of a viscous white oil were obtainedwhich crystallized on standing. This corresponds to a 36 moles percentyield based on the amount of hydratropaldehyde charged. The productconsisted of a 1:1 mixture of the two epimers of3,6-dihydro4,5-dimethyl-5-phenyl-u-pyrone previously referred to asepimer structures I and II.

Example 2 To a stirred three necked flask equipped with a refluxcondenser was charged 350 ml. of water and 10 gms. of sodium hydroxidepellets. Upon dissolution of the sodium hydroxide, 10 gms. ofhydratropaldehyde and 8.35 gms. of acetaldehyde were charged to thereactor. The reaction mixture containing acetaldehyde andhydratropaldehyde in a molar ratio of 2.5:1 was processed as in Example1.

The a-pyrone reaction product amounted to 6.3 gms. which corresponds toa 45 mole percent based on the hydratropaldehyde charged.

Example 3 To a three necked flask equipped as in Example 1 was charged175 ml. of water containing 5 gms. of dissolved sodium hydroxide, 7.0gms. of crotonaldehyde and 13.3 gms. of hydratropaldehyde. The reactionmixture containing crotonaldehyde and hydratropaldehyde in a molar ratioof 1:1 was refluxed at 98 to 100 C. for 1 hours. After cooling, thereaction mixture was neutralized with hydrochloride acid, etherextracted, dried over magnesium sulfate and the ether evaporated. 18.5gms. of crude product were obtained. Gas chromatographic analysis of thecrude product showed it to be 95.7 Weight percent of the desired cycliclactone mixture consisting of the two apyrone epimers obtained inExample 1. The ratio of the two epimers was approximately 2:1. Theepimer obtained by gas chromatographic separation methods as a solid,M.P. 93 C., occurred in the greater amount.

What is claimed is:

1. Epimeric mixtures of the lactone 3,6-dihydro-4,5-dimethyl-5-phenyl-a-pyrone having the formulas 4. A process for theproduction of an epimeric mixture of3,6-dihydro-4,S-dimethyl-S-phenyl-a-pyrone having the formulas whichcomprises reacting acetaldehyde or crotonaldehyde with hydratropaldehydeat reflux temperatures in the presence of a base, selected from thegroup consisting of alkali and alkaline earth metal hydroxides,carbonates and alkoxides wherein the mole ratio of acetaldehyde tohydratropaldehyde is about 1.5-2.5:1, or the mole ratio ofcrotonaldehyde to hydratropaldehyde is about 0.5- 1.5 1, and recoveringsaid u-pyrone.

5. The process according to Claim 4 wherein the mole ratio ofacetaldehyde to hydratropaldehyde is about 2:1.

6. The process according to Claim 4 wherein the mole ratio ofcrotonaldehyde to hydratropaldehyde is about 1:1.

7. The process according to Claim 4 wherein the reaction temperature isfrom about to C.

8. The process according to Claim 4 wherein the reaction product isneutralized with acid prior to recovery of the a-pyrone.

References Cited UNITED STATES PATENTS 2,514,325 7/1950 Fried 260343.5

DONALD G. DAUS, Primary Examiner A. M. T. TIGHE, Assistant Examiner US.Cl. X.R.

